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Red Cricket
Asked: 2013-12-04 14:55:24 +0800 CST

Why does dig succeed if I add an SOA query and fail when I do not?

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When I do this dig I get no answer...

red@localhost:~$ dig +noall +answer name-one.name-two.com @mydns-server.name-one.com

... but when add name-two.com soa I get an answer for name-one.name-two.com ...

red@localhost:~$ dig +noall +answer name-one.name-two.com name-two.com soa @mydns-server.name-one.com
name-one.name-two.com.   868     IN      A       xx.xxx.xxx.xxx
name-two.com.         2926    IN      SOA     ns41.name-three.com. dns.name-four.net. 2013120202 28800 7200 604800 600

... what is going on here?

Thanks

domain-name-system

1 Answers

  1. Best Answer

    Directly from dig -h:

    Usage:  dig [@global-server] [domain] [q-type] [q-class] {q-opt}
            {global-d-opt} host [@local-server] {local-d-opt}
            [ host [@local-server] {local-d-opt} [...]]

        [...]

        global d-opts and servers (before host name) affect all queries.
        local d-opts and servers (after host name) affect only that lookup.

    When you write: 

    dig +noall +answer name-one.name-two.com @mydns-server.name-one.com

    dig treats it as:

    +noall +answer
    - global options, applies to all queries

    name-one.name-two.com @mydns-server.name-one.com
    - host to lookup, at a specific name server

    But when you write: 

    dig +noall +answer name-one.name-two.com name-two.com soa @mydns-server.name-one.com

    dig treats it as:

    +noall +answer
    - global options, applies to all

    name-one.name-two.com
    - host to lookup

    name-two.com soa @mydns-server.name-one.com
    - another lookup for a SOA RR, but this time, at a specific server

    So the A RR response you receive for the first host is not from @mydns-server.name-one.com.

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